Typical hydrocarbon wells, whether on land or in water, are drilled into the earth's surface to form a well bore. A protective casing is run into the well bore and the annulus formed between the casing and the well bore is filled with a concrete-like mixture. Several types of tools are run into the casing for the various procedures used to complete and subsequently produce hydrocarbons from the well. Some of these procedures include perforating the casing and the concrete-like mixture. The perforating process creates channels into production zones of the earth at appropriate depths to allow the hydrocarbons to flow from the production zone through the casing and into production tubing for transport to the surface of the well. Another procedure includes gravel packing adjacent to the production zone to filter out in situ particles of sand and other solids from the production zone that are mixed with the hydrocarbons before the hydrocarbons enter the production tubing. Another procedure includes removing various tools to allow production of the well once it is completed.
Other tools and processes are needed to efficiently produce hydrocarbons including tools for filtration and separation of hydrocarbons from entrained water, tools that allow sealing of the well bore in case of explosion, rotating and drilling equipment in the well's initial phases, subsequent operations that can maintain the effectiveness and production of the well, and other related processes known to those with ordinary skills in the art, whether above or below the well surface. Most of the tools and related procedures require control of the various tools at appropriate stages of the operations.
Without limitation, one typical method of controlling the actuation of various tools at different stages includes the use of tools that have parts slidably engaged with each other. Often, although not necessarily, the parts are at first restrained from relative movement by the use of shear pins and other restraining devices. At an appropriate stage, the shear pins or other restraining devices are sheared or otherwise removed to allow a desired relative movement, such as actuation of the tool or for other purposes. Further, multiple sets of shear pins or other restraining devices can be used to implement multiple stages of actuation for the control system on the appropriate tool.
One typical method of actuation includes providing a ball seat on a tool. The ball seat is positioned in a passageway of tubing that can be used to create a flow blockage in the passageway. A ball or other obstruction can be placed in the passageway at an appropriate time to seat against the ball seat and effectively seal off the passageway. Fluid in the passageway that is blocked is then pressurized, creating an unequal force on the blocked portion of the tool. If present, a shear pin or other restraining device is sheared or otherwise removed and the tool portion moves into an appropriate position. Sometimes the movement can close or open ports, release or engage associated tools, change flow patterns and control fluids, and other functions known to those with ordinary skills in the art. For example, controlling fluids can include controlling a reversal of fluid flow caused by an unexpected downstream pressurization of production fluids.
However, one issue that has remained problematic is how to restrict the ball or other device from reversing up the passageway from the direction in which it entered the passageway once it has been placed on the ball seat. Further, some of the control logic of controlling the tool is lessened by the inability of the ball to seal in a reverse direction. For example, it could be advantageous to seal in one direction to effectuate one series of procedures and to seal in a reverse direction to control other procedures. Because the ball is typically inserted into a tubing passageway and generally flows downstream in the passageway to a remote site that has the ball seat, it has heretofore been difficult to construct a remote restraining device in the reverse direction.
In some prior efforts, some reverse direction restrictions have been attempted by providing a closely dimensioned upstream shoulder that the ball can be forced past, before engaging the downstream ball seat. At least two disadvantages occur with this method. First, the ball is not actively captured. A sufficient pressure reversal can force the ball back upstream and past the shoulder. The shoulder's ability to restrict a reverse travel is limited and does not correspond with the general strength of the tool to withstand various operating pressures.
Another procedure that has been used is to restrict reverse movement of the ball is to form a conical ball seat in the passageway. A ball placed in the passageway engages the conical ball seat and becomes wedged therein. However, similar problems occur in this type of seat. The ability to withstand a reverse pressurization in the passageway can be lower than tool's capabilities, because the ball can simply become dislodged back up the passageway.
Neither of the above arrangements actively control the ball in the reverse direction. The reversal control ability is simply dependent upon the original size and configuration, and thus the reverse control capabilities of the tools are limited.
Therefore, there remains a need to actively control and produce a fully capable control system associated with hydrocarbon wells.